The invention is based on an injection nozzle for internal combustion engines. In such injection nozzles, the course of injection has a first phase in which a preliminary injection of fuel is effected. In this first phase, the valve closing member executes its first stroke portion. Directly following the first phase is a second phase, corresponding to the second stroke portion of the valve closing member, in which the primary quantity of fuel is injected. The intention is to prolong the first phase to the greatest possible extent in order to improve idling and partial-load behavior, and to cause the valve closing member to return as rapidly as possible to its final position in the second phase, so that the primary fuel quantity can be injected quickly and completely. Upon the closure of this valve, the valve closing member should at first move rapidly back, but then be braked in good time so that shocks are avoided when the valve arrives at its valve seat.
In a known injection nozzle of this general type (Swiss patent No. 329 505, FIG. 4), the supplementary body is embodied by a support disk, which is displaceably disposed upon the valve closing member, which is embodied as a valve needle. The support disk is pressed by a supplementary spring against an annular collar of the valve needle, which acts in the opposite direction from the closing spring. At the end of the first stroke portion, the support disk strikes the stop attached to the housing in a form-locking manner, and the stop thereupon absorbs the supplementary spring force. During the second stroke portion, the force of the closing spring is thereby exerted completely against the valve needle. In this embodiment, it is true that an abrupt change is attained in the opening pressure or in the course of the valve return at the end of the first stroke portion of the valve closing member. However, it is disadvantageous that the two springs must be carefully matched to one another and that opportunities for exerting influence upon the course of injection are still limited.